The present invention relates generally to security systems, and more particularly to a vehicle system utilizing infrared communication and visible light for power coupling between a lock and key.
Current vehicle security systems typically include remote RF transmitters which transmit a security code to an RF receiver mounted on the vehicle. If a control module mounted on the vehicle recognizes the security code, the control module enables the ignition of the vehicle's engine. As is well known, the RF transmitted security code can be intercepted or "eavesdropped" by an unauthorized person with an RF receiver or a "code grabber." The unauthorized person can then later retransmit the intercepted code, unlocking the vehicle and enabling the ignition. As a result, many vehicle security systems have utilized complicated techniques involving encrypted or "rolling" security codes, in which, the RF transmitter continuously changes the security code. All RF transmitting systems have several other drawbacks. First, the RF transmitter must include a power source, such as a battery that degrades over time and must be replaced. Further, the RF signal can be jammed by RF or electromagnetic "noise," preventing operation of the RF system.
One known system utilizes an infrared transmitter on a key fob. An infrared receiver is typically mounted on the dome light or rearview mirror. The key fob transmits the security code to the infrared receiver, which then unlocks the vehicle. Although code grabbing is more difficult in this type of system, the security code can be intercepted by an unauthorized person. Further, the infrared transmitter includes a battery which degrades over time and must be replaced.
Another vehicle security system utilizes a small resistor mounted inside a key. When the key is inserted into the ignition lock, a circuit in the lock measures the resistance of the key. If the resistance value is recognized, the ignition is enabled. The system has two drawbacks. First, the electrical contacts on the key often wear out, become dirty or otherwise fail to make electrical contact with the lock, thereby preventing the owner of the vehicle from starting the engine. Further, unauthorized persons have developed keys having variable resistors which unlock any system of this type.
Another known vehicle system utilizes a small electronic circuit in a key which sends a coded signal via an RF transmitter built into the key. The RF transmitter is powered through electromagnetic coupling between the lock and the key. A coil on the lock provides an oscillating electromagnetic field which induces a current in a coil mounted in the key, thereby providing power to the RF transmitter. The RF transmission generated by this system can be intercepted as described above by unauthorized users. Further, the electromagnetic coupling which provides power to the key is relatively large, expensive and generates undesirable electromagnetic noise.